Aquaculture represents the fastest growing food-producing sector worldwide. However, the intensification of fish farms has led to environmental, health, and welfare challenges. The monogenean ectoparasite Gyrodactylus spp. has been considered one of the most pathogenic ectoparasites affecting fish, and no specific control strategies besides formalin baths have been established. The use of bioactive plants has been recently proposed as an alternative method to control gyrodactylid infections. Leucaena leucocephala is a tropical legume that has been found with anthelmintic activity against both internal and external parasites of cattle. Therefore, the objective of this study was to assess the anthelmintic-like activity of L. leucocephala aqueous extract against Gyrodactylus spp. in hybrid tilapia Oreochromis spp. fingerlings and its effect on host health through histopathological analysis. Five concentrations of L. leucocephala aqueous extract were employed (2.00, 1.00, 0.50, 0.25, and 0.125 mg/mL) to estimate the mean effective concentration (EC₅₀). Distilled water and formalin (1:4,000) were used as negative and positive controls, respectively. The aqueous extract of L. leucocephala showed a dose-dependent behavior, with an EC₅₀ of 0.228 mg/mL. Quercetin was identified as the main phytochemical present in the extract. Postmortem analysis of fingerlings exposed to the plant extract had no treatment-associated pathological findings, thus indicating that the use of L. leucocephala baths had no negative impact that could jeopardize the lives of treated animals. After the in vivo assessment, the aqueous extract of L. leucocephala appears to be a promising alternative to control gyrodactylid infection in tilapia.

中文翻译：

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银合欢水提取物对 Gyrodactylus spp. 的驱虫样活性。在自然感染的罗非鱼鱼种中

水产养殖是全球增长最快的食品生产部门。然而，养鱼场的集约化导致了环境、健康和福利方面的挑战。单系外寄生虫Gyrodactylus spp。已被认为是影响鱼类的最具致病性的外寄生虫之一，除福尔马林浴外，尚未建立任何特定的控制策略。最近有人提出使用生物活性植物作为控制 gyrodactylid 感染的替代方法。Leucaena leucocephala是一种热带豆科植物，已被发现对牛的体内和体外寄生虫具有驱虫活性。因此，本研究的目的是评估L的驱虫样活性。白头虫针对Gyrodactylus spp. 的水提取物。在杂交罗非鱼Oreochromis spp. 通过组织病理学分析鱼种及其对宿主健康的影响。L 的五种浓度。使用白头翁水提取物（2.00、1.00、0.50、0.25 和 0.125 mg/mL）来估计平均有效浓度 (EC ₅₀ )。蒸馏水和福尔马林 (1:4,000) 分别用作阴性和阳性对照。L的水提物。leucocephala表现出剂量依赖性行为，EC ₅₀0.228 毫克/毫升。槲皮素被确定为提取物中存在的主要植物化学物质。暴露于植物提取物的鱼种的死后分析没有与治疗相关的病理学发现，因此表明使用L . leucocephala浴没有可能危及经过治疗的动物的生命的负面影响。在体内评估后，L的水提取物。leucocephala似乎是控制罗非鱼 gyrodactylid 感染的有希望的替代方法。